The term usec appears in the
delay field of the
show interface command on a router:
Router# show interfaces fastethernet 0 Fast Ethernet0 is up, line protocol is up Hardware is DEC21140, address is 0000.0c0c.1111 (bia 0002.eaa3.5a60) Internet address is 10.0.0.1 255.0.0.0 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, rely 255/255, load 1/255 ^^^^^^^^^^^^
According to Wikipedia, a usec is a microsecond:
A microsecond is an SI unit of time equal to one millionth (0.000001 or 10−6 or 1/1,000,000) of a second. Its symbol is μs.
There are values associated with each interface, based upon the interface's speed:
- An ethernet (10 Mbps) interface has a delay of 1000 usec.
- A fast ethernet (100 Mbps) interface has a delay of 100 usec.
- A gigabit ethernet (1000 Mbps) interface has a delay of 10 usec.
In effect, the lower the delay usec, the higher the interface speed. But what is delay really measure of? What goes into the calculation to determine that a 100 Mbps link has a delay of 100 usec (and so on)?
It can't be the time it takes for a "bit" to cross the wire, because voltage applied to any interface speed traverses at the speed of light. It can't be a measurement of how many bits can be sent over a given time frame (because that is the Bandwidth measurement).
So what is usec really a measure of?